Many types of electronic devices have, such as mobile phones, handheld navigation devices, and portable media players, have an integrated, capacitive touch-screen for use as a display and user interface. When these types of devices are plugged-in to an AC power supply, such as to charge a battery of the device and/or to power the device, the AC power supply may generate common mode noise that causes display jitter and/or is sensed as a false touch input to the touch interface of the device. Capacitive touch interfaces are susceptible to electrical noise and other outside influences, which may cause erratic operation and inaccurate activations that can manifest as phantom or inaccurate touch inputs.
High common mode noise can be caused by a “noisy” AC/DC power supply or by other devices, such as a car dock that isolates an electronic device and creates a poor reference to ground. Other influences that can affect the performance of a capacitive touch interface are docking stations, car kits, HDMI and USB cables that are connected to a device, and other accessories that create an alternate or poor reference to ground. Many device manufacturers provide an AC/DC power supply (also commonly referred to as a wall adapter) that meets electronic device specifications to charge the battery of a device without introducing unwanted noise. For example, a manufacturer-provided AC/DC power supply may be designed for no more than a one (1) volt peak-to-peak maximum. When a user loses or misplaces the original equipment AC/DC power supply that is provided with a device, the user will typically replace the lost power supply with any one of many low-cost, aftermarket units that are available from any number of different sources. However, an aftermarket AC/DC power supply may allow as much as twenty-five (25) volt peak-to-peak common mode noise.